Role of CCL2/MCP-1 in mucosal immunity to Toxoplasma

描述(申请人提供)：弓形虫是一种主要的艾滋病相关病原体，可导致先天感染的婴儿严重疾病或死亡。该寄生虫也被归类为NIAID B类优先微生物。这项应用的长期目标是了解控制这种机会性原生动物病原体感染所必需的细胞免疫反应机制，并确定功能障碍的反应如何导致免疫病理和无法控制感染。初步数据表明，缺乏趋化因子MCP-1(CCL2)的小鼠对弓形虫的腹腔感染非常敏感，这与共表达Gr-1和MHC II类分子以及共刺激分子CD80/CD86和CD40的单核细胞/树突状细胞样群缺陷地重新聚集到腹膜有关。最近的其他研究也描述了类似的细胞，尽管它们是否介导保护或增加易感性尚不清楚，可能取决于感染模式。本研究的目的是确定在口腔弓形虫感染的黏膜免疫反应中，是否存在MHC-II和Gr-1(MHC2+Gr-1+)双阳性细胞。我们将用来解决这一问题的具体目标如下。1、确定口腔感染时CCL2缺乏与腹腔感染相比的影响，特别是趋化因子是否介导对弓形虫的耐药性或易感性，以及CCL2缺乏是否改变感染期间的Th1/Th2平衡。2、确定CCL2是否在黏膜对感染的免疫应答中招募MHC2+GR-1+细胞。这些细胞作为感染宿主的能力和表达杀菌分子和细胞因子(特别是IL-12)的能力也将被检测。这些目标将通过对从肠道粘膜组织中分离的细胞进行体外和体外分析来实现。在野生型和CCL2阴性小鼠的肠黏膜中，MHCⅡ类阳性细胞和Gr-1阳性细胞将通过荧光免疫组织化学直接显示。这些研究有望加深我们对弓形虫免疫是如何在粘膜组织中启动的理解，并将阐明MHC2+Gr-1+细胞在这一过程中的作用。了解免疫是如何触发的，最终将导致更有效地控制弓形虫和其他经口腔传播的艾滋病相关微生物病原体的感染。该项目与公共卫生的相关性在于，弓形虫感染了全世界30%-80%的人口。虽然通常是一种无症状感染，但由于免疫功能不佳，这种寄生虫会成为一种毁灭性的、有时甚至是致命的感染。该项目将加强我们对寄生虫免疫的了解，从而改进治疗策略。

DESCRIPTION (provided by applicant): Toxoplasma gondii is a major AIDS-associated pathogen that can cause severe disease or death in congenitally infected infants. The parasite is also classified as an NIAID Category B priority microorganism. The long-term objective of this application is to understand the cellular immune response mechanisms that are necessary to control infection with this opportunistic protozoan pathogen, and to determine how dysfunctional responses can lead to immunopathology and inability to control infection. Preliminary data indicate that mice lacking expression of chemokine MCP-1 (CCL2) are highly susceptible to intraperitoneal infection with T. gondii, and this is associated with defective recruitment into the peritoneal cavity of a monocyte/dendritic cell- like population co-expressing Gr-1 and MHC class II and costimulatory molecules CD80/CD86 and CD40. Other recent studies have described similar cells, although whether they mediate protection or increase susceptibility is not clear and may depend upon the infection model. The goal of the present proposal is to determine whether cells double-positive for MHC class II and Gr-1 (MHC2+Gr-1+) are recruited during the mucosal immune response to oral infection with Toxoplasma. The specific aims we will employ to address this issue are as follows. 1, Determine the effects of CCL2 deficiency during oral infection compared to intraperitoneal infection, in particular whether the chemokine mediates resistance or susceptibility to Toxoplasma, and whether lack of CCL2 alters the Th1/Th2 balance during infection. 2, Determine if CCL2 recruits MHC2+GR-1+ cells during the mucosal immune response to infection. The ability of these cells to serve as an infection reservoir and to express microbicidal molecules and cytokines (in particular, IL-12) will also be examined. These aims will be achieved by ex vivo and in vitro analyses of cells isolated from intestinal mucosal tissues. Direct visualization of MHC class II-positive and Gr-1-positive cells in intestinal mucosa of wild-type and CCL2 negative mice will be accomplished by fluorescence immunohistochemistry. These studies can be expected to deepen our understanding of how immunity to Toxoplasma is initiated in mucosal tissues and will clarify the role of MHC2+Gr-1+ cells in this process. Understanding how immunity is triggered will ultimately lead to more effective means of controlling infection with Toxoplasma and other orally transmitted AIDS-associated microbial pathogens. The relevance of the project to public health is that Toxoplasma infects between 30-80% of the human population worldwide. While normally an asymptomatic infection, with suboptimal immune function the parasite emerges as a devastating and sometimes lethal infection. This project will enhance our understanding of immunity to the parasite, leading to improved treatment strategies.